1. Field of the Invention
The present invention relates to a washing machine, and, more particularly, to a drum type washing machine having ball balancers and a controlling method of the same that are capable of reducing spin-drying time.
2. Description of the Related Art
Generally, a washing machine is an electric home appliance, including a water tub to store water (wash water or rinse water), a wash tub rotatably mounted in the water tub to receive laundry, and a wash motor to generate a drive force necessary to rotate the wash tub, to lift the laundry in the wash tub along the inner wall of the wash tub and drop the lifted laundry, during the rotation of the wash tub, thereby washing the laundry.
In recent years, there has been a drum type washing machine constructed in a structure in which a drum is mounted in a machine body such that a rotary shaft of the drum is parallel to the bottom of the machine body, and laundry is lifted and dropped, during the rotation of the drum, such that the laundry collides with wash water, and therefore, the laundry is washed. The drum type washing machine washes laundry such that the laundry is less damaged than other washing machines, with the result that the drum type washing machine is becoming popular among users.
In such a drum type washing machine, however, the rotary tub, in which the laundry is placed, is horizontally disposed, with the result that the rotary tub is rotated at high speed, while laundry is collected on the bottom of the rotary tub due to gravity, during a spin-drying operation. Consequently, the center of gravity of the laundry does not coincide with the center of rotation of the rotary tub, with the result that there is a great possibility of vibration and noise. To solve the problem, the conventional drum type washing machine includes ball balancers mounted in the rotary tub to maintain the dynamic balance of the rotary tub.
When the drum type washing machine having the ball balancers performs a spin-drying process using a centrifugal force generated by the high-speed rotation of the rotary tub, the rotary tub is vibrated to induce noise in an unbalanced state in which laundry placed in the rotary tub makes a lump at one side. For this reason, it is preferred to perform a spin-drying operation in a balanced state in which the laundry is uniformly distributed in the rotary tub.
To perform the spin-drying operation in the balanced state, the conventional drum type washing machine having ball balancers is operated to rotate the rotary tub to an eccentricity detection rotation speed, detect the eccentricity amount of the rotary tub while rotating the rotary tub at a constant speed, when the detected eccentricity amount is less than an allowable eccentricity amount, accelerate the rotary tub to a ball balancer position estimate speed, estimate the positions of the ball balancers while rotating the rotary tub at a constant speed, decide a point of time for spin-drying acceleration using the estimated positions of the ball balancers, and spin-drying accelerate the rotary tub at the decided point of time for spin-drying acceleration.
In the conventional drum type washing machine having ball balancers as described above, however, the rotary tub is rotated at a constant speed for a predetermined period of time to estimate the positions of the ball balancers, and then the rotary tub is spin-drying accelerated. As a result, water rising along the outside of the rotary tub by the rotating force of the rotary tub during the constant-speed rotation of the rotary tub continue to rise along the outside of the rotary tub even during the spin-drying acceleration of the rotary tub. The water rising along the outside of the rotary tub is drained later out of the water tub, with the result that spin-drying time increases.
Also, in the conventional drum type washing machine having ball balancers as described above, the rotary tub is accelerated to the predetermined speed, and the generation of vibration from the rotary tub is detected using the rotation speeds of the rotary tub before and after the acceleration. As a result, the generation of vibration from the rotary tub is not detected when the rotary tub is not accelerated.